Priority flow control valve

ABSTRACT

A flow control valve in a hydraulic system having a single source of pressurized fluid. The flow control valve provides priority of flow for predetermined actuators and pressure control for a plurality of hydraulic actuators.

United States Patent Inventor James R. McBumett Stillwater, Okla.

Appl. No. 877,934

Filed Nov. 19, 1969 Patented Aug. 10, 1971 Assignee Allis-ChalmersManufacturing Company Milwaukee, Wis.

PRIORITY FLOW CONTROL VALVE 10 Claims, 1 Drawing Fig.

US. Cl 60/52 VS, 60/52 S lnt.CI FlSb 1-1/16 Field oISearch............60/52 VS, 52 S [56] References Cited UNITED STATES PATENTS 2,737,1963/1956 Eames 60/528 X 2,799,995 7/1957 Herman 60/52 S X 2,892,311 6/1959VanGerpen 60/52 S 2,892,312 6/1959 Allen et a1. 60/52 S 3,429,123 2/1969Burroughs 60/52 VS X 3,446,020 5/1969 Stephens et al 60/52 VS PrimaryExaminer-Edgar W. Geoghegan Attorneys-Arthur L. Nelson, Kenneth C.McKivett and Robert B. Benson ABSTRACT: A flow control valve in ahydraulic system having a single source of pressurized fluid. The flowcontrol valve provides priority of flow for predetermined actuators andpressure control for a plurality of hydraulic actuators.

Patented Aug 10, 1971 PRIORITY FLOW CONTROL VALVE a plurality of pumpsare used to supply pressurized fluid to one or more. of the fluidactuators in the system. A -plurality of pumps are generally usedprimarily because of the various flow rates and various pressuresdemanded by the hydraulic actuators in the system. A plurality of pumpsmay become costly as well as presenting a space problem, or a driveproblem in operating the various pumps. Accordingly, a single source ofpressurized fluid may be used if provisions are madefor priority of flowto the actuators which require priority to I maintain safety inoperation of the vehicle and also a pressure control must also be usedto provide the required pressure for operating each hydraulic actuatorin the system.

Accordingly this invention provides a single source of pressurizedfluid. Preferably the source of pressurized fluid is a 2 The pilot linefrom the plurality of actuators controls the displacement of the pumpand supplies the pressure requirements of the highest load operated byany of the hydraulic actuators in the system.

The preferred embodiments of this invention will be illustrated anddescribed. The attached drawing illustrates the priority flow control.valve with the hydraulic actuators and the pump illustratedschematically. I

Referring to drawing the priority control valve 1 is illustrated incross section. The valve 1' is connected to the variable displacementpump 2 by the conduit 3. The priority flow control valve is alsoconnected by the conduit 4 to the sump 5.

variable displacement pump having a compensator to sense '7 pressure andload demands in the system. A compensator is in communication with apluralityof pilot lines sensing the load of each hydraulic actuator inthe system which'is fed back to the compensator which regulates the pumpto provide the highest pressure demanded in the system. The priority offlow is controlled through a priority control valve to maintainpriority'of flow for safety in operation of the vehicle. Ac-

cordingly, along with priority of flow the provision of supply- I ingpressurized fluid at the proper pressure for any operation demanded isalso included.

It is an object of this invention to provide a single source ofpressurized fluid in a hydraulic system serving a plurality of hydraulicactuators at a plurality of pressures.

It is another object of this invention to provide a flow and pressurecontrol valve in a closed center load sensitive hydraulic system.

It is a further object of this invention to provide a priority 2 flowand pressure control valve with a reducing valve to provide the desiredpressure as well as priority of flow to a plurality of hydraulic fluidactuators.

It is a further object of this invention to provide priority of flow ata predetermined pressure to the power takeoff, differential lock, andthe brake actuators and priority of flow to the steering hydraulicactuator at a predetermined second pressure and simultaneously providepressurized fluid to a draft control valve in a load sensitive closedcenter hydraulic fluid system.

v The objects of this invention are accomplished with a variabledisplacement pump having a compensator sensing the load requirements ofa draft control valve and a remote valve such as power steering. Thevariable displacement pump, although operating in a hydraulicsystemnormally considered a closed center system,.provides continuouscirculation to the steering hydraulic actuator with a bypass valvedelivering pressurized the steering circuit also hasa control-to operatethe steering manually'in the eventof power failure which requirescommunication to a fluid'reservoir or sump. The draft control valve hasa low priority. and receives fluid in response to operation attltepressure responsive plunger.

The conduit 4 receives fluid from the sump 5 which can flow through thecheck valve 6 in evcnt of power failure. The fluid flowing through theconduit 4 supplies fluid to the steering mechanism 7 including amanually operated hydraulic valve 8. The valve 8 is of the typeillustrated in the originally copending application of the same assigneeentitled "Hydraulic Steering System" now issued as-U.S. Pat. No.3,528,521.

The pump 2 also is connected-by a drain conduit 9 which is immersedunder the oil level of the sump 5. A supply conduit 10 is connected tothe pump 2 and supplies fluid to the pump 2 as the pump is operating.The pump 2 also includes a compensator ll which senses a pressure signaland strokes or destrokes the pump in accordance with the load demands ofthe various hydraulic actuators in the system. A compensator 11 isconnected to these various hydraulic actuators through the pilot line12. The draft control pilot line 13, steering pilot line 50, a checkvalve 17 in the draft control'pilot line 13, and check valve 51, allpermit transmission of a pilot pressure signal from the hydraulicactuators. The highest pilot signal controls the operation of thecompensator 11 which in turn control the stroking and destroking of thepump and accordingly the demands of the hydraulic system are met.

The discharge side of the pump 2 delivers pressurized fluid to theconduit 3 and the connection 21 of the priority flow control valve. Thepassage 22 delivers pressurized fluid to the priority flow control valve1 while the connection 21 is also connected to the conduit 23 which inturn delivers pressurized fluid to the pressure limiting valve 24. Thepressure limiting valve is set for'a predetermined pressure required bythe actuators on the downstream side of the pressure limiting valve 24.For the purpose of illustration it will be assumed that the hydraulicactuators downstream from the pressure limiting valve 24 will operate atapproximately 250 psi.

The conduit 25 delivers pressurized fluid from the pressure limitingvalve 24 to the conduit 26. The valve 27 and the conduit 26 controls theflow of pressurized fluid to the hydraulic actuators 28 in the powertakeoff assembly 29. The valve 27 is schematically illustrated althougha more complete illustration and description of this type of valve andits operation with the power takeoff may be had by referring to theoriginally copending patent application of the same assignee now U.SPat. No. 3,507,372 which covers a hydraulic clutch an brake system for apower takeoff assembly. The operation of the power takeoff assembly isprovided through a clutch and a brake which control the delivery ofpower to the power takeoff shaft and are operated in response to a valvemeans to provide the desired function.

Conduit25 is also connected to conduit 30 which includes a valve 31 anddelivers pressurized fluid to the actuator 32 in the differentialassembly 33. A more complete illustration of the differential assemblyand its operation may be had be referring to the US. Pat. No. 3,446,320which covers a differential lock and the means forcontrolling theactuation of the differential lock through a relay valve operated inresponse to braking of the vehicle.

The conduit 25 is also connected to a conduit 34 which includes a valve35 which controls the actuation of the hydraulic actuator 36 of thebrake assembly 37.

The pressure limiting valve 24 limits the pressure of the pressurizedfluid delivered to the power takeoff, the differential lock, and thebrake. Normally the pressurized fluid applied to these circuits is in astandby condition and hydraulic fluid is not flowing to the hydraulicactuators. The pressurized fluid, however, must be available in eventthat it is needed to operate any of the actuators in these three operations.

The priority flow control valve 1 includes a housing 40 having a centralopening 41 receiving the plunger 42v The plunger 42 is biased to anupward position by the spring 43 to seat against the valve seat 44. Theplunger 42 defines an orifice 4S permitting the flow of pressurized flowinto the hollow portion of the plunger 42. A plurality of radialorifices 46 permit the flow of pressurized fluid into the annularchamber 47 defined by the housing 40 of the flow control valve. Theannular chamber 47 is in communication with the pilot passage 49 whichis connected by the pilot line 50 to the pilot line 12. The check valve51 permits the flow of pressurized fluid to the pilot line 50 when thepilot pressure in the chamber 47 exceeds the pilot pressures of theremote hydraulic actuators previously described.

The steering supply line 52 also is in communication with the annularchamber 47 and supplies pressurized fluid to the hydraulic steeringvalve 8 and actuator 100. The hydraulic steering valve is connected tothe steering mechanism in such a manner whereby the steering wheel 53controls a valve element 101 for driving the steering mechanism ineither direction in response to direction of rotation of the steeringwheel 53. This in turn provides power steering of the steering mechanismof the vehicle.

When pressurized fluid is in the steering supply conduit 52 apredetermined amount of pressurized fluid flows through the orifice 45and the orifices 46 to supply the steering valve 8. For the purpose ofillustration the flow rate will be considered to be 4 gallons per minutewhich is adequate for steering of the vehicle. The bypass valve 54shunts the steering valve 8 and bypasses fluid around the valve 8 whenthe fluid is not required to operate the motor 100. The bypass valve 54is biased to a closed position by the spring 55 and opened in responseto pressurized fluid operating in the passage 56. Fluid flowing throughbypass valve 54 passes through the conduit 57 and through the filter 58.A fluid cooling device 59 cools the fluid and returns i to the sump 5.The filter and cooler have bypass means to prevent pressure buildup andlack of pressure drop across the steering motor. A constant circulationthrough the steering circuit is provided even though pressurized fluidis not demanded for steering. it provides cooler operation of the pump 2and cools and filters the hydraulic fluid in the system for betteroperation.

The valve 8 is mechanically connected to the wheel 53 and in event ofpower failure rotation of the wheel itself will operate the valve as apump as long as fluid is present in the steering supply conduit 52.Fluid in the steering conduit 52 and chamber 47 is connected to thechamber 60 which receives fluid through the check valve 6 from conduit4. The conduit 4 may be connected to any low-pressure source of fluidmerely to maintain the presence of fluid in the system for manualoperation in the event of power failure.

The flow control valve 1 further defines a passage 61 con- I nected tothe conduit 62 and the draft control valve 63. The

draft control valve 63 is operated in response to a draft load sensed onthe linkage 64. This load produces a force signal transmitted throughthe linkage to the lever 65 which in turn operates the valve 63. Amanual lever 66 can also operate the draft control valve 63 when desiredsuch as for lifting the implement and changing the implement from fieldoperating position to the transport position. The draft control valve 63supplies pressurized fluid to the hydraulic actuator 67 for weightdistribution of the tractor and implement and also will provide forlifting of the implement to the transport position when desired. Theload on the hydraulic actuator 67 is sensed by the pilot line 13 andtransmitted to the pilot line 12 where it is sensed by the compensator11.

A detailed and complete illustration and description may be had for adraft control valve and its operation relative to the implement byreference to the Strehlow U.S. Pat. No. 2,679,199. Essentially theStrehlow device operates in a manner as briefly described above, whichsets forth the function in relation to the priority control valve.

A preferred embodiment of this invention has been illustrated anddescribed and operation will be set forth in the following paragraphs.

Referring to the drawing a typical illustration of the valve'is shown inthe normal operating position. Before the engine is started the plunger42 is in its uppermost position blocking the oil passage to the draftcontrol valve. Oil for manual steering operation is provided through theconduit 4 to the manual steering check valve 6 through the variableorifice 46 and finally through the steering supply line 52. The steeringwheel operates a motor which will provide steering of the vehicle andthe motor will operate as a pump to operate the hydraulic actuatorconnected to the steering linkage.

When the engine is started the pump 2 pressurizes fluid which flowsthrough the orifice 45 until the pressure drop across the orifice 45 inthe plunger 42 is sufficient to begin to move the plunger downwardlyagainst the spring 43. The flow rate at this time will be slightly lessthan the desired steering flow rate of approximately 4 gallons perminute. As the flow rate continues to increase due to increasing speedof the engine the flow rate through the orifice 45 will continue toincrease until the pressure drop across the orifice 45 plus the pressuredrop across the orifice 46 is approximately 250 psi. At this point thepump 2 will always adjust its displacement to maintain this flow rateindependent of speed. The typical position of plunger 42 will be thatshown in the drawing. Notice that the oil passages to the draft controlvalve and the remote valves are open even though no fluid is flowing tothese valves at this time. The flow rate to the steering circuit is alsoindependent of required steering pressure. This pressure is monitored bythe steering pilot signal line. The flow rate to the steering circuit isalso independent of the draft control or remote pressures whether thesepressures are higher or lower than the pressure required for steering.if these pressures are higher than required steering pressure plunger 42will shift downwardly in its bore and throttle the excess pressureacross the variable orifice 46. If these pressures are lower thanrequired steering pressure, the plunger will shift upward in its boreand throttle the oil flow to the draft control valve.

The draft control operates in response to a pressure signal receivedfrom the draft sensing unit through the linkage 64. The linkage 64provides automatic operation of the draft control valve 63. The pressurein the system required by the draft control valve 63 and hydraulicactuator 67 is sensed by the pilot line 13 and fed back to thecompensator 11 through the conduit 12. The compensator senses thepressure and will increase or decrease the operating pressure asdemanded by the draft control valve 63 to provide sufficient flow ofpressurized fluid for the system.

The power takeoff actuator, the differential lock actuator, and thebrake actuator all operate independently through the pressure limitingvalve 24 which is set for the purpose of illustration at 250 psi. Thisis the standby pressure at which the hydraulic actuators in these remoteoperations will normally operate. Their operation is in response toactuation of the valve controlling their operation. The valves areillustrated schematically and will be normally controlled by theoperator of the vehicle. When a valve is open the fluid flowing throughthe valve operates the hydraulic actuator it controls while the pressurelimiting valve 24 admits the flow of fluid and maintains the pressure atthe preset value.

lt can be seen that the hydraulic system with the priority flow controlvalve as set forth above eliminates any need for additional gear pumpsto operate the plural functions set forth in this system. The steeringcircuit is supplied with pressurized fluid at all times and also has theprovision for filtering and cooling. This provides a cooler running pumpin the hydraulic circuit and provides greater overall efficiency in thesystem. A minimum pressure level of 250 psi. is assured for the powerytakeoff, the differential lock,

and the brakes even when high flow is dfemanded by the draft control orremote valves. The system is simple and yet flexible in providing aplurality'of aux- .iliary operations from a single load sensitivevariable displacement pump.

The preferred embodiments of this invention have been illustrated anddescribed.

The embodiments of the invention in which I claim an exclusive propertyor privilege is claimed and defined as follows:

1. A pressure and flow control device for use in a hydraulic system,including a variable displacement pump with a compensator sensing loadpressure, said device comprising, a priority flow control valve, inletconduit means on said flow control valve adapted for connection to saidpump, a pressurelimiting valve connected to said inlet conduit means andadapted for'connection on the downstream side of said pressure limitingvalve to a plurality of remote hydraulic actuators, a draft controlvalve connected to said priority flow control valve, a steering circuithaving a hydraulic control and actuator connected to said priority flowcontrol valve, a pressure responsive element normally limitingcommunication between said pump and said draft control valve, orificemeans on 'said pressure limiting means regulating priority flow ofpressurized fluid to said steering circuit, a plurality of pilot linesadapted for connection to the hydraulic actuators on said circuit andconnected to the compensator of said pump sensing load preswherein oneof said remote hydraulic actuators includes an actuator for operating abrake.

5. A pressure and flow control device as set forth in claim 1 whereinsaid hydraulic system includes, a sump connected to said pump, a fluidsupply conduit connected to said sump including a check valve connectedto said priority flow control valve to permit fluid flow from said sumpthrough said priority wherein one of said remote hydraulic actuatorsincludes a 1 hydraulic actuator for a differential lock.

4; A pressure and flow control device'as set forth in claim 1 flowcontrol valve to said steering circuit in event of power failure of saidpump. I

6. A pressure and flow control device as set forth in claim 1 whereinsaid pressure responsive element in said priority flow control valvedefines a valve preventing communication to said draft control valvewhen said pump is inoperative.

7. A pressure and flow control device as set forth in claim 1 whereinsaid pressure responsive element of said priority flow control valvedefines an orifice axially positioned in said element for throttlingpressurized fluid, means on said element define radially positionedthrottling orifices throttling flow of pressurized fluid to form avariable area orifice in said priority flow control valve, said housingdefining a fluid chamber in communication with said radial orifices andsaid steering circuit to thereby provide throttling of pressurized fluidflowin through said priority valve to said steering circuit.

8. A pressure and flow control-device as set forth in claim 1 whereinsaid steering circuit includes a filter receiving continuous flow ofpressurized fluid from said pump through said steering circuit, a bypassvalve and a hydraulic actuator selectively transmitting hydraulic fluidthrough said steering circuit..

9. A pressure and flow control device as set forth in claim 1 whereinsaid steering circuit includes a fluid cooler for hydraulic fluidthereby cooling hydraulic fluid flowing through said steering circuit tothereby cool the pressurized fluid in said hydraulic system.

10. A pressure and flow control device as set forth in claim I whereinsaid steering circuit includes a bypass valve operating at apredetermined pressure to bypass fluid around said steering motor tothereby permit constant flow through said steering circuit.

1. A pressure and flow control device for use in a hydraulic system,including a variable displacement pump with a compensator sensing loadpressure, said device comprising, a priority flow control valve, inletconduit means on said flow control valve adapted for connection to saidpump, a pressure-limiting valve connected to said inlet conduit meansand adapted for connection on the downstream side of said pressurelimiting valve to a plurality of remote hydraulic actuators, a draftcontrol valve connected to said priority flow control valve, a steeringcircuit having a hydraulic control and actuator connected to saidpriority flow control valve, a pressure responsive element normallylimiting communication between said pump and said draft control valve,orifice means on said pressure limiting means regulating priority flowof pressurized fluid to said steering circuit, a plurality of pilotlines adapted for connection to the hydraulic actuators on said circuitand connected to the compensator of said pump sensing load pressures andcontrolling displacement of said pump through said compensator andcontrolling the flow and pressure of pressurized fluid in said system,said priority flow control valve thereby providing regulated priorityflow to said steering circuit and standby pressure with flow control tosaid remote hydraulic actuators and said draft control valve.
 2. Apressure and flow control device as set forth in claim 1 wherein one ofsaid remote hydraulic actuators Includes an actuator for a power takeoffassembly.
 3. A pressure and flow control device as set forth in claim 1wherein one of said remote hydraulic actuators includes a hydraulicactuator for a differential lock.
 4. A pressure and flow control deviceas set forth in claim 1 wherein one of said remote hydraulic actuatorsincludes an actuator for operating a brake.
 5. A pressure and flowcontrol device as set forth in claim 1 wherein said hydraulic systemincludes, a sump connected to said pump, a fluid supply conduitconnected to said sump including a check valve connected to saidpriority flow control valve to permit fluid flow from said sump throughsaid priority flow control valve to said steering circuit in event ofpower failure of said pump.
 6. A pressure and flow control device as setforth in claim 1 wherein said pressure responsive element in saidpriority flow control valve defines a valve preventing communication tosaid draft control valve when said pump is inoperative.
 7. A pressureand flow control device as set forth in claim 1 wherein said pressureresponsive element of said priority flow control valve defines anorifice axially positioned in said element for throttling pressurizedfluid, means on said element define radially positioned throttlingorifices throttling flow of pressurized fluid to form a variable areaorifice in said priority flow control valve, said housing defining afluid chamber in communication with said radial orifices and saidsteering circuit to thereby provide throttling of pressurized fluidflowing through said priority valve to said steering circuit.
 8. Apressure and flow control device as set forth in claim 1 wherein saidsteering circuit includes a filter receiving continuous flow ofpressurized fluid from said pump through said steering circuit, a bypassvalve and a hydraulic actuator selectively transmitting hydraulic fluidthrough said steering circuit.
 9. A pressure and flow control device asset forth in claim 1 wherein said steering circuit includes a fluidcooler for hydraulic fluid thereby cooling hydraulic fluid flowingthrough said steering circuit to thereby cool the pressurized fluid insaid hydraulic system.
 10. A pressure and flow control device as setforth in claim 1 wherein said steering circuit includes a bypass valveoperating at a predetermined pressure to bypass fluid around saidsteering motor to thereby permit constant flow through said steeringcircuit.